Production Of Gold Bars, Ögussa GmbH Factory, Vienna, Austria

Standard bar weights
Gold is measured in troy ounces, often simply referred to as ounce when the reference to gold is evident. One troy ounce is equivalent to 31.1034768 grams.
Commonly encountered in daily life is the avoirdupois ounce, an Imperial weight in countries still using British weights and measures or United States customary units. The avoirdupois ounce is lighter than a troy ounce; one avoirdupois ounce equals 28.349523125 grams.
The standard gold bar held and traded internationally by central banks and bullion dealers is the Good Delivery bar with a 400 oz. nominal weight. However, its precise gold content is permitted to vary between 350 oz and 430 oz. The minimum purity required is 99.5% gold. These bars must be stored in recognized and secure gold bullion vaults to maintain their quality status of Good Delivery. The recorded provenance of this bar assures integrity and maximum resale value.